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lint-rules-android.md

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  • AlertDialogUsage - Support library AlertDialog is much more powerful and plays better together with the new theming / styling than the AlertDialog built into the framework.
  • AssertjImport - Importing org.assertj.core.api.Assertions is not ideal. Since it can require Java 8. It's simple as instead org.assertj.core.api.Java6Assertions can be imported and provides guarantee to run on Java 6 as well.
  • ColorCasing - Colors should have uppercase letters. #FF0099 is valid while #ff0099 isn't since the ff should be written in uppercase.
  • ConstraintLayoutToolsEditorAttribute - The tools:layout_editor xml properties are only used for previewing and won't be used in your APK hence they're unnecessary and just add overhead.
  • DefaultLayoutAttribute - Flags default layout values that are not needed. One for instance is the textStyle="normal" that can be just removed.
  • ErroneousLayoutAttribute - Flags if a layout attribute is not applicable to a particular view.
  • FormalGerman - Informal language should be used at all times.
  • ImplicitStringPlaceholder - It's better and more explicit to use numbered placeholders.
  • InvalidAccessibility - Marks usages of invalid accessibility and suggests corrections.
  • InvalidImport - Flags invalid imports. One example is com.foo.bar.R.drawable. Instead just the generated class R should be imported and not R.drawable. Also you should never import anything that's in an internal package.
  • InvalidSingleLineComment - Single line comments should always be sentences. They're part of the code and hence they deserve as much detail and respect as code.
  • InvalidString - A translation string is invalid if it contains new lines instead of the escaped \n or if it contains trailing whitespace.
  • JCenter - JCenter has gotten less and less reliable and it's best to avoid if possible. This check will flag usages of jcenter() in your gradle files.
  • LayoutFileNameMatchesClass - Layout file names should always match the name of the class. FooActivity should have a layout file named activity_foo hence.
  • MatchingMenuId - When the layout file is named menu_home all of the containing ids should be prefixed with menuHome to avoid ambiguity between different menu files across different menu items.
  • MatchingViewId - When the layout file is named activity_home all of the containing ids should be prefixed with activityHome to avoid ambiguity between different layout files across different views.
  • MissingScrollbars - Every scroll view should explicitly define whether it has scrollbars (none | vertical | horizontal).
  • MissingXmlHeader - An xml file should always have the xml header to declare that it is an xml file despite the file ending.
  • NamingPattern - Sometimes there is more than one reasonable way to convert an English phrase into camel case, such as when acronyms or unusual constructs like "IPv6" or "iOS" are present. XML HTTP request becomes XmlHttpRequest. XMLHTTPRequest would be incorrect.
  • Quotes - It's better to replace them with their appropriate quotes in each language.
  • RawColor - Color value should all be defined as color resources. This has the benefit that you can easily see all of your colors in one file. One benefit is an easier addition to Dark Theme for instance. This check will run on layouts as well as xml drawables.
  • RawDimen - Dimensions should all be defined as dimension resources. This has the benefit that you can easily see all of your dimensions in one file. One benefit is that when designers change the outline across the entire app you only have to adjust it in one place. This check will run on layouts as well as xml drawables.
  • ResourcesGetColorCall - Instead of getColor(), ContextCompat or the method with the Theme Overload should be used instead.
  • ResourcesGetColorStateListCall - Instead of getColorStateList(), ContextCompat or the method with the Theme Overload should be used instead.
  • ResourcesGetDrawableCall - Instead of getDrawable(), ContextCompat or the method with the Theme Overload should be used instead.
  • ShouldUseStaticImport - Certain declarations like TimeUnit.SECONDS should be statically imported to increase the readability.
  • StringNotCapitalized - Every string should be capitalized. If not, it is flagged.
  • SuperfluousMarginDeclaration - Instead of using start-, end-, bottom- and top margins, layout_margin can be used.
  • SuperfluousNameSpace - Re-declaring a namespace is unnecessary and hence can be just removed.
  • SuperfluousPaddingDeclaration - Instead of using start-, end-, bottom- and top paddings, padding can be used.
  • Todo - Marks todo in any given file since they should be resolved.
  • UnsupportedLayoutAttribute - Some layout attributes are not supported. Your app will still compile but it makes no sense to have them around. This can happen when refactoring a LinearLayout to a ScrollView. The orientation is no longer needed and can be removed.
  • UnusedMergeAttributes - Adding android, app and other attributes to won't be used by the system for custom views and hence can lead to errors.
  • WrongAnnotationOrder - Annotations should always be applied with the same order to have consistency across the code base.
  • WrongConstraintLayoutUsage - Instead of using left & right constraints start & end should be used.
  • WrongDrawableName - The drawable file name should be prefixed with one of the following: animated_selector, animated_vector_, background_, ic_, img_, notification_icon_, ripple_, selector_, shape_, vector_. This will improve consistency in your code base as well as enforce a certain structure.
  • WrongGlobalIconColor - In order to reuse icons, it's best if all icons share the same color and can be used at every position in the app. On the target side, tinting can be applied.
  • WrongLayoutName - The layout file name should be prefixed with one of the following: activity_, view_, fragment_, dialog_, bottom_sheet_, adapter_item_, divider_, space_, popup_window_. This will improve consistency in your code base as well as enforce a certain structure.
  • WrongMenuIdFormat - Menu ids should be in lowerCamelCase format. This has the benefit of saving an unnecessary underscore and also just looks nicer.
  • WrongTestMethodName - The @Test annotation already states that this is a test hence the test prefix is not necessary.
  • WrongViewIdFormat - View ids should be in lowerCamelCase format. This has the benefit of saving an unnecessary underscore and also just looks nicer.
  • XmlSpacing - Having newlines in xml files just adds noise and should be avoided. The only exception is the new lint at the end of the file.